Abstract: This invention provides a defragmentation utility that works on-line in parallel with other file system activities. Thus, it avoids making the file system unavailable for periods of time which would, if not for this invention, slow down data communication exchange and the execution of other tasks dependent upon the data. In particular, this invention, steps through all of the valid inodes finding each of the fragments. The defragmentation engine decides which fragments must remain in their current location and which fragments should migrate to another disk block sub-block location. Since the data blocks span across multiple disks, for each valid disk of the file system a set of disk blocks are constructed that are chosen to be filled, herein called plates. When the plates become full or reach a certain fullness, they are removed from the set and replaced by other disk blocks. When a disk block is removed from the plate set, it is moved to a “done” list as it is considered “full”.

Abstract: A method is provided for limiting access to disks and files in the event of a system partitioning occurring as the result of a node failure in a data distributed processing system in which files are shared amongst a plurality of independently running nodes. The nodes in the system are provided with limited duration leases which permit data access and which have to be periodically renewed. Each partition is also associated with a quorum which is also a necessary element in providing access at proper times. The lease and quorum concepts work together to insure that recovery operations do not occur until recovery is possible. The lease concept thus is also seen as further operating in close cooperation with the quorum concept to prevent long delays in the recovery process that could otherwise occur.

Abstract: A method is provided for continuing node operations in quorum-based protocols. This is particularly valuable in the situation in which a group of nodes includes only two nodes and in which communications to a node is lost. Provision is made for adding additional status indications to each node indicating whether or not it is enabled for single-node quorum operation. Provision is also made for identifying one node as a primary node and another node as a secondary node for time-out response purposes.

Abstract: A computer system having a shared disk file system running on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. Locking techniques reduce the overhead of a token manager which is also used in the file system recovery if a computer participating in the management of shared disks becomes unavailable or failed. Synchronous and asynchronous takeover of a metadata node occurs for correction of metadata which was under modification and a new computer node to be a metadata node for that file. Locks are not constantly required to allocate new blocks on behalf of a user.

Abstract: A computer system having a shared disk file system running on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. Methods are provided for use as a parallel file system in a shared disk environment by use of a scaleable directory service for the system with a stable cursor, and a segmented allocation map. Dynamic prefetch and cached balance pools for multiple accesses improve the system. Extended file attributes are used for implementation of Access Control Lists in a parallel file system. A metadata node manages file metadata for parallel read and write actions. For our system, tokens are used for metadata node selection and identification. We have provided recoverable local shares for quota Management.

Abstract: A computer system having a shared disk file system running on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. Methods are provided for use as a parallel file system in a shared disk environment by use of a scalable directory service for the system with a stable cursor, a segmented allocation map. Dynamic prefetch and cached balance pools for multiple accesses improve the system. Extended file attributes are used for implementation of Access Control Lists in a parallel file system. Improvements to caching and cache performance developments balance pools for multiple accesses. A metadata node manages file metadata for parallel read and write actions.

Abstract: A computer system having a shared disk file system running on on multiple computers each having their own instance of an operating system and being coupled for parallel data sharing access to files residing on network attached shared disks. Methods are provided for use as a parallel file system in a shared disk environment by use of a scalable directory service for the system with a stable cursor, a segmented allocation map. Synchronous and asynchronous takeover of a metadata node occurs for correction of metadata which was under modification and a new computer node to be a metadata node for that file. Locks are not constantly required to allocate new blocks on behalf of a user. We have provided recoverable local shares for Quota Management. A quota server and a quota client are provided for each file system, and a quotacheck utility allows parallel environments with minimal interference to other applications which require the use of quotas.

Abstract: A vehicle lift has a support platform and a pair of scissor mechanisms underneath it for supporting it, and raising and lowering it. An actuator, for example, an hydraulic cylinder, that is connected between the scissor arms. The ends of one pair of scissor arms include rollers for engaging the ground, the rollers permitting the lift to be raised and lowered. A cart or other lifting device is provided for lifting one end of the lift, to support it on wheels of the cart. With the other end of the lift supported on the rollers of the scissor arms, the lift can be freely moved around on a flat surface. The lift can have a simple ratchet locking mechanism including a cam, which provides a simple mechanism for locking the lift in a raised position, and for enabling it to be lowered.

Abstract: A plate, for use in adjusting the rear wheels of a four wheel vehicle incorporating all wheel steering has an elongate sheet-form bearing cage, which includes a plurality of apertures. Ball bearings or other rolling elements are located in the apertures, and a top sheet member is located on top of the ball bearings. In use, the ball bearings are supported on a horizontal planar surface, for example a support platform of a hydraulic lift or a separate base sheet member. The configuration of the cage and the bearings is such that the top sheet member is capable of limited lateral and rotational movement in a horizontal plane, to permit full adjustment of rear wheels of a vehicle having a steering capacity.

Abstract: A lifting apparatus has two posts on either side. A lifting or cross member extends between them and is supported on carriages slidably mounted on the posts. Support arms or the like extend out from the support carriages for supporting a vehicle or other load. Actuators are provided for driving the carriages up and down. The actuators can be hydraulic cylinders connected in a master and slave relationship with a hydraulic connection between them through the cross member. Additionally, mechanical safety catches can be provided which are connected by a cable or the like through the cross member, to permit a single handed operation of them. In the further aspect of the invention, a mechanism is provided for locking the support arms angularly, which mechanism includes plungers that contact the ground and automatically free the support arms when the apparatus is lowered.